Berlin 2001 – wissenschaftliches Programm
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Q: Quantenoptik
Q 2: Poster: Generation of Short Pulses
Q 2.4: Poster
Montag, 2. April 2001, 12:30–15:00, AT2
Femtosecond soliton bulk Er:Yb:glass laser — •G. Wasik, F. W. Helbing, F. König, A. Sizmann, and G. Leuchs — Lehrstuhl für Optik, Physikalisches Institut, Universität Erlangen-Nürnberg, Staudtstr. 7/B2, 91058 Erlangen
A bulk solid state Er:glass laser can combine the advantages of existing Er:fiber lasers, i.e. operation in the femtosecond regime, with the flexibility of free-space resonators, which provide improved pulse-width tunability at the telecommunication wavelength around 1.5 µm. In order to achieve ultrashort pulses we use soliton modelocking, i.e. a balance between dispersion and nonlinearity in the resonator. The nonlinearity of the resonator is enhanced by sandwiching the Er:glass at the beam waist between two 9.5-mm fused silica glass plates which serve as an additional Kerr medium. The dispersion is adjusted by a pair of fused silica prisms. Using an output coupler of 1.7% transmission yielded pulses as short as 600 fs (τFWHM) with an average output power of Pav=60 mW (at total incident pump power of 600 mW) at the repetition rate of 100 MHz. To increase the intracavity intensity and to obtain in this way stronger self-phase modulation, i.e. to decrease the pulse length, we exchanged the output coupler by a highly reflecting mirror (T≈0.1%). As a result, the pulse length shortened to 380 fs. Independent of the laser parameters, the pulses are Fourier-limited with the average time-bandwidth product of 0.320±0.013. The pulse duration can be varied form 600 fs to 4 ps by varying the dispersion. We found a good agreement between the measurements and the soliton model prediction: the product τFWHM· Pav is proportional to the group velocity dispersion.